The wear and tear of a racing pigeon, can lead to so many problems. So observation at all times on how the individuals is a must, what we can see outside may be a different story on the inside.
https://www.youtube.com/watch?v=NLEigoQtNV0
The racing pigeons heart.
Last year my old pigeon Gordon raised a pair of foster babies for my mate David. Take your pick, he said, so I kept one and he took the other. A month or so later his one was flying and dropped dead out of the air. 
All he said was "should have took the other one".
Seriously though, as a rule racing pigeons have strong hearts. They have to.This is where I think breeding from flown pigeons is better than pigeons that have spent their lives locked up. Here in Australia I have stock birds that have flown all their lives but you can't train or race them, the hawks get them. They still loft fly and they need to fly hard and fast like the race birds.
But in New Zealand birds that were bought in for stock still had all the tosses out to about 50 miles to see if they were physically and mentally up to the job.
You get the odd one with a great pedigree but isn't strong enough. Hard to tell when they are sitting in a cage looking beautiful.
All he said was "should have took the other one".
Seriously though, as a rule racing pigeons have strong hearts. They have to.This is where I think breeding from flown pigeons is better than pigeons that have spent their lives locked up. Here in Australia I have stock birds that have flown all their lives but you can't train or race them, the hawks get them. They still loft fly and they need to fly hard and fast like the race birds.
But in New Zealand birds that were bought in for stock still had all the tosses out to about 50 miles to see if they were physically and mentally up to the job.
You get the odd one with a great pedigree but isn't strong enough. Hard to tell when they are sitting in a cage looking beautiful.
Greetings from the land down under. 
Blessed is he who expecteth nothing, for verily, he shall not be disappointed.
Blessed is he who expecteth nothing, for verily, he shall not be disappointed.